Bi-level switching of lighting loads enables building occupants to manually reduce the lighting load to facilitate energy conservation, occupant comfort, etc. Most states have adopted energy conservation codes that require some form of bi-level switching to provide building occupants the ability to reduce lighting loads by at least 50 percent in a reasonably uniform pattern. Some states have adopted energy conservation codes that demand even higher levels of energy conservation. For example, Title 24 of the California Code of Regulations requires that at least one of the lighting loads in a bi-level switching system must only be turned on manually.
One recognized method for bi-level switching involves controlling all of the lamps in a room with a common dimmer or multi-level power switching to enable the power to all of the lamps in the room to be reduced uniformly. Thus, the term bi-level switching may also be understood to also refer to methods involving multi-level switching or dimming. A second method involves dual switching alternate rows or groups of light fixtures, lamps within fixtures, etc. A third method is specific to 3-lamp lighting fixtures and involves separately switching the inner and outer lamps in one or more fixtures. A fourth method involves providing a separate switch or control for each lamp or light fixture in a room.
Although energy conservation codes specify how lighting systems must work at a high level, they provide no guidance on the actual implementation details. Moreover, energy conservation codes only specify minimum levels of functionality and energy conservation.